You can add two different SCB-based UART components to a project schematic when using this chip, and they can operate independently on different sets of pins. If you want to connect more than two UART devices, or you do not want to use multiple SCB components, then you will need to use an external UART MUX chip with GPIO-based routing selection. However, in this case, you would not be able to communicate with more than one UART device at a time.